Process for the production of thionyl chloride



Patented June 7, 1932 UNITED STATES PATENT OFFICE, I

WALTER S. BEANBLOSSOMQOF NIAGARA. FALLS, NEW YORK, A SSIGNORTTOI-HOOKEB ELECTROCHEMICAL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF 'YQRK rnocnss non THE rnonncrronlor r -rionyn cnnonr nn N'o Drawing. Application filed April 10,

The present invention relates to processes for the production of thionyl chloride.

Several processes for the preparation of thionyl chloride already have been proposed, but they appear to be attended by certain disadvantages: in some cases, relatively costly chemicals are required; in others undesirable phosphorus compounds contaminate the product; and in carrying out certain of the 1 known processes pressure vessels are required. l

The present invention has for its object the provision of an economical, safe, simple process for the production of relatively pure thionyl chloride free from phosphorus compounds, and requires only relatively cheap starting materials.

The above, and other, objects of invention have been attained by treating sulfuric acid with sulfur dichloride,or a substance which yields sulfur dichloride upon treatment with chlorine,and with chlorine.

In carrying out the process of thepresent invention, sulfur dichloride isslowly added, with stirring, to sulfuric acid in a suitable vessel, at atmospheric pressure while introducing chlorine gas into the mixture, and the mixture is gently heated, with stirring, while being kept saturated with chlorine gas, until a homogeneous reaction mixture is produced. Thereafter the content of thionyl chloride is separated from the reaction mixture by an appropriate procedure, such as, for

instance, distillation.

In order to minimize or avoid losses due to the escape of vapors, it is desirable to maintain the temperature at as low a point as is possible consistent with the production of thionyl chloride. To this end, it has been 40 found that the reaction may be effected at satisfactorily low temperatures by carrying out the same in the presence of a relatively small but effective amount of a suitable catalyst such, for instance, as mercuric chloride, antimony trichloride or chlorides of various inthe distillate, may be re-e-mployed in a 1930. Serial no. 443,247.

other heavy metals. The use of such a catalyst not only admits of effecting the -reaction at lower temperatures but alsohasthe desirable resultof accelerating the speed of reaction. r j 50 The followingequation may be assumed to represent the course of the reaction:

2H SO +3SCl5+Cl ZSOChfi-lSOytfH-IQI The invention willbe described more par ticularly by reference to the following illus trative exampleof a typical embodiment thereof, it being understood, nevertheless, that the invention is not limited to the specific conditions and proportions therein stated: 40 partso -f'sulfuric acid (100%) andOgfL parts of 'mercuric chloride are placed ina suitable vessel and, While maintaining the temperature below 30C., 735 parts of sulfur 5,5 dichloride. is added, with constant stirring, while introducing chlorine gas intothe mixture.- The contents are then refluxed' ata temperature of from to C. untila homogeneous mixture is produced, the reaction mixture being. kept saturated with chlorine gas throughoutthe heating. The resulting mixture thereafter is distilled, yieldinga distillate containing about38 parts of thionyl chloride with atrace of sulfur di- I chloride, and a residue of acid containing the catalyst. Theflsaid residue,.as well as any sulfur-dichloride which may be present succeeding charge- I v It ispreferable, although not essential, that sulfuric acid be employed, the

waterpresent in a weaker acidffavoring. de-j composition of. the product. As will have become apparent frorn thefi foregoing, theremay be substituted forthe sulfur dichloride asubstanfce capableiof producing the sulfur dichloride upon; tre tment with chlorine,the total amount of chlorine used being correspondinglyaincreased, and itfi? is to be understood therefore, that the invention embraces such a substitution.

Thus, for example, in lieu of the direct addition of sulfur dichloride to the sulfuric acid there may be added sulfur or sulfur monochloride either of which yields sulfur dichloride when treated with chlorine in accordance with the following equations:

S 01 +CI ==QSCI I claim: I 1. Process ofproducing thionyl'chloride, which comprises treating sulfuricacid with sulfur dichloride and chlorine, and separating the so-formed thionyl chloride from the resulting reaction mixture by distillation.

2. Process of producing thionyl chloride,

whichcomprises adding sulfur dichloride to sulfuric acid slowly and with constant agitation while introducing chlorine gas into the below 30 C. with eonstant agitation while maintaining it saturated with chlorine gas,

and separating the so-formed thionyl chloride from the resulting reaction mixture by distillation, e

3. process of producing thionyl chloride, which comprises slowly adding sulfur dichloride to sulfuric acid at a temperature below 30, C. with constant agitation whileintroducing chlorine gas into the mixture, heating themixture under reflux'at a temperatureof from to 70 0., while maintaining it saturated with chlorine gas, until ahomogeneous reaction mixture is obtained and separating the so-formed thionyl chloride from the reaction mixture by distillation.

4. Process of producing thionyl chloride, which comprises slowly adding sulfur dichloride to 100% sulfuric acid at a temperature below 3090. with constant agitation while introducing chlorine gas into themixture,

heatingthe mixture under refiux'at a temperature of from 50 to 70 0., while main t'aining it saturated with chlorine gas, until a homogeneous reaction mixture is obtained,

' and separating the so-formed thionyl chlochloride of a metal of the group including ride. from the reaction mixture by distillation. 5. Process as claimed in claim 1, in which the reaction is effected in the presence of a relatively small'but effective amount of catalytically acting heavy metal chloride.

V 6. Process as claimed in claim 1, in which the reaction is effected in the presence of a relatively small'but effective amount of a mercury and'antimony.

7 Process as claimed in claim 1, in which the reaction is effected in the presence of a relatively small but effective amount-of mercuric chloride.

In testimony whereof, I affix my signature.

WALTER s. BEANBLOSSOM. I 

